You could have asked yourself when flipping thru magazines why all the models have always clearly erected nipples when shot with tight or transparent shirts, while the women you see in the street are rarely that excited.

The answer is of course that the photographer asked them to appear so. After a few times, he doesn't have to, since the model knows by herself what is expected from her. Sometimes she would use ice, nonchalantly left in a glass on the table near her, as if ice cubes were a standard accessory in make-up; and sometimes she'll discretely use her hands.

Now, if she's not a model but a superstar, she isn't expected to do anything by her own hands, even not play with her breasts. Therefore the stylist assistant will oblige, generally without mentionning it, as if he/she is just arranging the outfit. The others - photographer, PR, fashion editor, assistants etc - will pretend not to notice what's going on. After a few minutes, he/she will have to play with the star's nipples again. Photo sessions are real downers.

Now, if she's not just any superstar but the one and unique Jennifer Lopez, she will have a professional nipple tweaker. In the pic above (bigger version here), you can see him at work (white shirt, the guy in the black sweatshirt is playing only with her hair). J.Lo then asked him to slide up his hand under her net T-shirt.

The results of his efforts can be clearly noticed here. Dozens of bystanders in L.A. watch the star then performing for the camera till the effect slowly disappeared. The star then got another treatment, not forgeting to take a sip from her helper. The clip, by the way, is for a new album called "This is me... now". Yeah, tell me about it.